
public class BinarySearchTree {
    static class TreeNode {
        public int val;
        public TreeNode left;
        public TreeNode right;

        public TreeNode(int val) {
            this.val = val;
        }
    }

    public TreeNode root=null;

//    查找二叉搜索树中指定k
    public TreeNode search(int key) {
        TreeNode cur=root;
        while(cur!=null) {
            if(cur.val<key) {
                cur=cur.right;
            }else if(cur.val>key) {
                cur=cur.left;
            }else {
                return cur;
            }
        }
        return null;
    }

    public void insert(int val) {
        //所有的插入最后都是叶子结点
        //不能插入两个相同的数据
        TreeNode node=new TreeNode(val);
        if(root==null) {
            root=node;
            return;
        }
        TreeNode cur=root;
        TreeNode parent=null;
        while(cur!=null) {
            if(cur.val<val) {
                parent=cur;
                cur=cur.right;
            }else if(cur.val>val) {
                parent=cur;
                cur=cur.left;
            }else {
                return;
            }
        }
        //while循环走完后，指向的节点就是需要插入的节点位置的父亲节点
        if(node.val<parent.val) {
            parent.left=node;
        }else if(node.val>parent.val) {
            parent.right=node;
        }
    }

//    节点删除
    public void remove(int key) {
        TreeNode parent=null;
        TreeNode cur=root;
        while(cur!=null) {
            if(cur.val<key) {
                parent=cur;
                cur=cur.right;
            }else if(cur.val>key) {
                parent=cur;
                cur=cur.left;
            }else {
                removeNode(parent,cur);
                return;
            }
        }
    }

    private void removeNode(TreeNode parent,TreeNode cur) {
        if(cur.left==null) {
            if(cur==root) {
                root=cur.right;
            }else if(cur==parent.left) {
                parent.left=cur.right;
            }else {
                parent.right=cur.right;
            }
        }else if(cur.right==null) {
            if(cur==root) {
                root=cur.left;
            }else if(cur==parent.left) {
                parent.left=cur.left;
            }else {
                parent.right=cur.left;
            }
        }else {
            TreeNode target=cur.right;
            TreeNode targetP=cur;
            while(target.left!=null) {
                targetP=target;
                target=target.left;
            }
            cur.val=target.val;
            if(target== targetP.left) {
                targetP.left=target.right;
            }else {
                targetP.right=target.right;
            }
        }
    }
}
